A colorless heat-sensitive transfer recording paper having pressure-sensitivity composed of a substrate sheet, a heat-sensitive recording layer provided on a front surface of the substrate sheet, and a layer provided on a back surface of the substrate sheet consisting of a microcapsuled electron donative colorless color-former, an electron acceptive developer which develops with the color-former, the solid color-former and developer and waxes is known to the art (Japanese Patent Kokai Publication No. 168690/1985). However, in the recording papers of this class, since the layer provided on a back surface of the substrate sheet contains both a color-former and a developer, even if weak handling pressure is applied to the material, the microcapsule may easily rupture, and pollution due to color development may occur. Furthermore, since a number of compositions have to be provided onto the same substrate sheet, the amount of coating becomes relatively large, susceptibility to pressure and heat is remarkably reduced, and good recording and copy typing may not be obtained.
To overcome these problems, a pressure- and heat-sensitive multilayer copying paper comprising a combination of: an upper paper member composed of a substrate, a heat-sensitive layer provided on a front surface of the substrate, and a transfer layer provided on a back surface of the substrate comprising a colorless color-former, a microcapsuled color-former and a thermomeltable material; and a lower paper member having an image receiving layer thereon (Japanese Kokai Patent Publication No. 90232/1987) is proposed. For using the pressure- and heat-sensitive multilayer copying paper, the upper paper member is stacked on the lower paper member, and heat is applied onto a surface thereof by the use of, for example, a thermal head, and thereby, thermal printing may be obtained on the heat-sensitive layer provided on a surface of the upper paper member, as well as a thermomeltable material of the pressure- and heat-sensitive transfer layer is melted and transferred to the lower paper due to the thus applied heat energy. The thermomeltable material co-melts with a developer provided on a front surface of the lower paper member to form heat duplicated print. When no pressure is applied, only heat duplicated print is formed, but when pressure is applied simultaneously or independently, a microcapsule provided on the back surface is broken due to the applied pressure, and a color-former encapsulated is transferred to a front surface of the lower paper member to form pressure print. The pressure- and heat-sensitive multilayer copying paper of this class is suitable for use in a portable terminal printer and the like. However, preferred clear and deep print may not be provided, because a front surface of the lower paper member is apt to be polluted by a slight pressure which is applied to the paper during handling or transporting.
The present invention overcomes these problems in the pressure- and heat-sensitive multilayer copying paper noted above. As a result, an object of the present invention achieved by placing an overcoated protective layer comprising a UV curable resin over the pressure- and heat-sensitive transfer layer comprising a color-former, a microcapsuled color-former and a thermomeltable material.